Many electrical systems utilize an amplifier to charge a switched capacitor. Conventional amplifiers are designed to charge the capacitor to a particular capacitance. However, if the charging time is fixed to a short period, an amplifier needs to be set to operate at high speed to suit the electrical charging time. If an amplifier is set to operate at high speed, a wide range of thermal noise is amplified raising the noise of the amplifier circuit. While methods to reduce noise level exist, such as including an adding function at the amplifier output, these methods have the undesirable effect of increasing the circuit size and increasing the calculation period.